Grease guns are used, as is well known, to provide grease to an appropriate fitting which, in turn, conveys the grease to a bearing or other movable part which is to be lubricated. The fitting generally has a one-way valve in order to allow ingress of the grease and to retain the grease in the fitting after it has been provided to the fitting by the grease gun.
Typically, such grease guns are manually operated. That is, following attachment of the hose to the fitting, the handle of the gun is manually operated while holding the cartridge housing in the other hand. Thus, a two-handed operation is necessary to force the grease from the gun to the fitting. Such two-handed operation can be inconvenient.
A further inconvenience with present grease guns and other extrusion devices is that air can be trapped in the piston bore which forces the grease through the one-way valve, which valve usually is a check valve retained on a shoulder in a passageway by the use of a compression spring downstream from the flow. In the event that air is trapped in the passageway, it is necessary to use a bleed valve to remove the air in order to continue operating the apparatus. This, too, can be inconvenient since a further operation to open the bleed valve is required.